A Roadmap to Evolution of Self-Organising LTE-Advanced Cellular Networks

Dr. Hafiz Yasar LateefResearch Scientist

Outline• The Transition From Conventional Network Operation to Self-

Organising Networks (SON)

• Self-Organising Networks Use Cases and Functional Scope

• Self-Organising Functions Interdependencies & Conflicts

• Self-Coordination Framework

• Trigger-Condition-Action Policy for MRO & MLB

• Future Work

Conventional Cellular Networks

Fig. 1. Manual Network operation of Cellular Networks

Manual Network Operation

Next Generation Cellular Networks

Fig. 2. Network Management with Closed-Loop Automation

Cellular Networks Planning Cycle

Fig. 3. Network Planning, Optimisation & Operation Cycle

NGMN Recommendations for SON

Fig. 4. Overview of the NGMN Top Operational Efficiency Recommendations for SON

SON Standardisation in 3GPP

Fig. 5. Roadmap for SON Standardisation in 3GPP (Courtesy of [7])

Fig. 6. RAN2 & RAN3 activities (Courtesy of [7])

SON Standardisation in 3GPP

SON Standardisation in 3GPP

Fig. 7. SA5 activities (Courtesy of [7])

High Level Operational Life Cycle without SON Co-ordination

Fig. 8. High Level Operational Life Cycle of Cellular Networks (Courtesy of [7])

High Level Operational Life Cycle with SON Co-ordination

Fig. 9. High Level Operational Life Cycle of Cellular Networks with SON Co-ordination (Courtesy of [7])

SON Use Cases

Fig. 10. Self-configuration, Self-Optimisation & Self-healing Use Cases

Super KPI & Business Impact

Qualitatively, the overall performance of the network can be described by a ‘Super KPI’ like

P = x . “Coverage” + y . “Capacity” + z. “Quality”

where the weights x, y, and z depend on the business targets of the operator as well as on specific area, maturity of the network layer, time of day, and so on.

Autonomous Networks & SON

Fig. 11. Autonomous networks & SON

Role of SON Functions in Operation & Maintenance of Cellular Networks

Fig. 12. Location of SON Functions in 3GPP OAM Architecture

SON Functional Scope

Fig. 13. SON Functional Spatial Scope Vs SON Function Spatial Execution

Self-Organising Functions Inter-DependenciesSO functions may have complex relations and parameter/logical inter-dependencies which can induce conflicts among SO functions and eventually undermine the network operation.

Fig. 14. Shared Configuration Parameters between different SON Functions

• Therefore, coordination among SO functions is essential for not only to avoid objective/parameter conflicts but also to ensure the stable operation of wireless networks.

• It is also vital to figure out the optimum way of designing Self optimization algorithms in conjunction with self co-ordination for efficient radio resource management and reduced operational expenditures (OPEX).

SON Conflicts Classification

Self-Organising Function Conflicts

Fig. 15. Conflict between CCO & ICIC SO functions.

• SO functions conflicts are categorised into the following five primary categories:

• (A) Key Performance Indicator Conflict; • (B) Parameter Conflict;• (C) Network Topology Mutation Conflict; • (D) Logical Dependency Conflict; • (E) Measurement Conflict.

SON Conflicts Classification

• NTM: Network Topology Mutation

SON Conflicts Classification

• Network topology mutation conflict occurs due to the change in network conditions by addition/ removal of eNB/ HeNB/ Relay.

• HeNBs are frequently switched on/off or relocated which will continuously disturb the optimum configuration of SO functions.

• Similarly, mobile relays can effect coverage area in a random pattern and will cause a NTM conflict for CCO function.

Mobility Load Balancing

Fig. 16. Mobility Load Balancing-Traffic Steering Decisions

Mobility Load Balancing

Fig. 17. Negotiation of Handover Parameters (Courtesy of [7])

SON Conflict Resolution

Fig. 18. Conflict between Mobility Load Balancing & Mobility Robustness Optimisation (Courtesy of [7])

• Trigger-Condition-Action (TCA) based policy is quite useful in designing conflict free SO functions as it provides a holistic picture of all the possible triggers, SO functions conflicts, necessary conditions to be checked and the corresponding actions to be executed.

• TCA policies are the keys to design conflict free “decision tree logic” or “joint optimisation algorithms” for SO functions such as MRO, MLB, CCO and EE.

Trigger-Condition-Action Policy

MLB Trigger Condition-Action Policy

MRO Trigger Condition-Action Policy

• Most of the previous research work has focused on intra-frequency connected mode handover condition for MRO.

• However, MRO function for inter-frequency, inter-RAT handover conditions in both connected and idle mode has been unrevealed.

• More specifically, optimum configuration of CIO, TTT, filter co-efficient, cell reselection thresholds and priorities for inter-frequency, inter-RAT handover conditions in both connected and idle mode needs to be identified.

Future Research Challenges

• It must be mentioned here that most of the previous research work has focused on intra-frequency connected mode mobility load balancing.

• However, MLB function for inter-frequency, inter-

RAT cases in connected, idle and transition mode has been unrevealed.

• More specifically, optimum configuration of CIO, TTT, filter co-efficient, BB thresholds and absolute priorities for inter-frequency, inter-RAT mobility load conditions in connected, idle and transition mode needs to be identified.

Future Research Challenges

• If self optimisation and self co-ordination functions are executed independently, then the algorithm part of self optimisation functions will always be executed irrespective of the subsequent acknowledgment or rejection of the action request by the Self Co-ordination function.

• Moreover, based upon the rejected action requests, numerous self optimisation algorithms might have been executed without any performance gains.

• The above mentioned facts drive for finding optimum interactions between self optimisation and self co-ordination functions.

Optimum Interactions Between Self Optimisation & Self Co-ordination Functions

References1. Hafiz Yasar Lateef, Ali Imran, Adna Abu-dayya, “A Framework for Classification of

Self-Organising Network Conflicts & Coordination Algorithms,” submitted to PIMRC’ 13.

2. Osianoh Glenn Aliu, Ali Imran, Muhammad Ali Imran and Barry Evans. " A Survey of Self Organisation in Future Cellular Networks", Accepted in IEEE Journal of Survey and Tutorials on Communications.

3. 3GPP TS 32.500, "Telecommunication management; Self-Organizing Networks (SON); Concepts and requirements," v. 10.0.0, June 2010.

4. NGMN, "Recommendation on SON and O&M Requirements," Requirement Specification, www.ngmn.org, version 1.23, Dec. 2008.

5. NGMN, "Use cases related to Self Organising Network, Overall Description," White Paper, www.ngmn.org, version 2.02, Dec. 2008.

6. 3GPP, "TR 36.902 - Self-configuring and self-optimizing network (son) use cases and solutions,". Technical Specification, 2010.

7. Seppo Hämäläinen Cinzia Sartori, Henning Sanneck. "LTE Self-Organising Networks (SON): Network Management Automation for Operational Efficiency". WILEY, 2011.

Thank You!